Search results for ""verlag g. mainz""
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Verlag G. Mainz Novel Acceleration Methods and Improved Transition State Finding Approaches for the Automatic Exploration of Reaction Networks
Reaction models are important for many engineering tasks, such as the optimization of internal combustion engines or production lines in the chemical industry. The automated reaction space exploration method ChemTraYzer attempts to alleviate the often time-consuming reaction model development process. ChemTraYzer uses reactive Molecular Dynamics (rMD) simulations to find the underlying reactions of the reaction process. Coupling the rMD output to quantum-mechanical reoptimizations of reactant, product and transition state (TS) geometries and to transition state theory, allows ChemTraYzer to produce kinetic and thermochemical data with the low uncertainties,which are required for many reaction model applications. In this thesis, I address two major issues of the ChemTraYzer method. First, I introduce two acceleration techniques for the rMD simulations, the pressure-accelerated Dynamics (pAD) and ChemTraYzer-Temperature-Accelerated Dynamics (ChemTraYzer-TAD) methods, to extend the app
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Verlag G. Mainz Optimization of LowCarbon Energy Systems from Industrial to National Scale
Climate change mitigation requires a reduction of greenhouse gas (GHG) emissions. The main emitter of GHG emissions is the energy sector, which today is based on fossil fuels. To mitigate climate change, we need to transform the energy systems to low-carbon technologies. For this purpose, new energy system designs are required along with appropriate operational strategies. In principle, these new designs and operational strategies can be identified best using mathematical optimization. However, low-carbon technologies impose challenges in solving and assessing the resulting optimization problems.Low-carbon technologies are volatile, which increase the complexity of optimal synthesis and operation. To cope with the complexity of operational optimization, we develop a time-series decomposition method. The method decomposes the complex, time-coupled operational problem into smaller subproblems, while still providing feasible, near-optimal solutions. For the increased complexity
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Verlag G. Mainz Advances in NMR spectoscopy and imaging
Nuclear Magnetic Resonance (NMR) techniques have proliferated in many fields of science and technology like bio-sensing, chemical reaction monitoring and material characterization. Since the inception of NMR as an analytical tool, improving the sensitivity by increasing the field strength has been the primary development goal. However, in order to reduce cost and environmental impact, the trend to miniaturized NMR devices and its diverse application fields enjoys increasing interest. The first part of this thesis introduces novel insights into low-power rf-excitation, which is one crucial aspect for enabling further development in this direction, by employing Frank sequences. Based on experimental data, a detailed evidence of the power savings by excitation in the linear regime is given aiming at future elimination of the rf-amplifier from the NMR spectrometer so as to allow further mobility improvements. Selective excitation by colored Frank-sequence is reported, which bears promis
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Verlag G. Mainz Reliable and Robust Optimal Design of Sustainable Energy Systems
The synthesis of energy systems is a complex task, since a plethora of conditions needs to be regarded during decision making. Thus, mathematical optimization is an excellent tool to accomplish this task and to identify an optimal system design. However, energy system synthesis is intrinsically uncertain, since the availability of components is inherently uncertain as well as the input parameters, such as energy demands. As a result, neglecting uncertainties might lead to a lack of energy supply. An insufficient energy supply possibly causes both high unexpected costs and environmental damage. Thus, uncertainties need to be regarded during optimization of energy systems. At the same time, sustainability is a further major aspect in the synthesis of energy systems. To regard sustainability performance, multiple decision criteria, such as economic, environmental, and social criteria, need to be taken into account. For this purpose, employing multi-objective optimization is perfectly s
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Verlag G. Mainz Monoand Tetranuclear Complexes Featuring OSSO or TrisONNOType Ligands for Selective Catalysis
Whereas tetradentate (OSSO)-type ligands mostly allow for the preparation of mononuclear transition metal complexes, lignads that feature two or more of the structurally related (ONNO)-type subunits may give access to multinuclear heterometallic complexes. +IV, +V and *VI stabilized by tetradentate (OSSO)-type ligands led to the development of a tris(ONNO)-type ligands revealed a new approach toward heterometallic 3d transition metal complexes that resolves the limitations of core/shell template directed synthesis and avoids metal cooperative effects resulting in magnetic interactions of the paramagnetic center and in enhanced catalytic activity in transformations of heterocumulenes with epoxides. This thesis further contributes to the field of mono- and tetranuclear metal complexes stabilized by (OSSO)- or tris(ONNO)-type ligands. Based on these ligands, the stractural, magnetic and electrochemical propeties of various complexes are reported.
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Verlag G. Mainz Technology Choice Model for Consequential Life Cycle Assessment
Consequential Life Cycle Assessment (CLCA) aims at capturing the environmental consequences of decisions such as the introduction of a new technology, the implementation of a policy, or the purchase of a product. CLCA combines technical and economic modeling approaches to track the consequences of decisions throughout the economy, considering both technical relationships within industrial production systems and market-mediated effects. However, although CLCA is well defined at a conceptual level, a commonly accepted modeling framework for CLCA is still missing, leading to wide differences in CLCA practice.To promote the systematization of the CLCA approach, this thesis proposes a comprehensive modeling framework for CLCA: the Technology Choice Model (TCM). Compared to existing approaches, TCM captures market-mediated effects in multiple markets at a substantially higher level of technical detail, while systematically considering constraints in factor availability, uncertainty
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Verlag G. Mainz PhysicallyBased Models for the Analysis of Raman Spectra
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Verlag G. Mainz GoalOriented Optimal Experimental Design for Reactive Chemical Systems
For the design and control of chemical processes, models that can accurately describe the physicochemical interactions of the process are needed. However, even with systematic modeling frameworks, the validation of predictive models is time and cost consuming. The generation of experimental data required for model validation often ensues in considerable effort and costs, which can be reduced via optimal experimental design (OED) methods. This thesis addresses the question on how to obtain predictive models for reactive complex chemical processes with the least experimental effort for a given application.The different challenges encountered during modeling complex reactive systems are discussed in Chapter 2. To this end a tutorial is presented for modeling chemical systems exhibiting dynamics on different time scales owing to fast (equilibrium-limited), and slow (kinetically-limited) reactions. The presented systematic modeling approach, complementing existing literature, is b
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Verlag G. Mainz Optimizationbased Process Screening of Biorefinery Pathways at Early Design Stage
In order to increase sustainability of chemical processes, a raw material change from conventional to renewable feedstocks is the key. This opens up numerous novel process concepts. A detailed conceptual design of all of these different pathways is expensive and time-consuming, since the mandatory simulations depend on pre-specified design decisions and commercial simulation software lack robustness. Hence, screening methodologies are required for an initial assessment of the processes. Existing screening methods are restricted to reaction or process design data known in literature, such that the integration of novel pathways requires simulation studies. This is impeded by limited data availability and the lack of profound property models.Process Network Flux Analysis is introduced as an optimization-based screening methodology to accelerate process development and improvement for existing and novel processes. The method systematically integrates reaction data with the select
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Verlag G. Mainz Biohybrid Catalysts for Alkene Metathesis
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Verlag G. Mainz Debottlenecking the Evaporator in WaterBased Adsorption Chillers
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Verlag G. Mainz A Modelbased Framework for Optimal Systems Integration of Adsorption Chillers
The global demand for cooling increases and poses a challenge for the stability of electrical grids and the emission targets. Thermally-driven adsorption chillers can meet this challenge by substituting electricity with thermal energy. However, although adsorption chillers are primarily driven by thermal energy, practical experience shows that the electricity savings often hardly compensate the electricity demand of the auxiliaries, such as pumps and fans. Thus, smart systems integration is crucial. Systems integration of adsorption chillers is challenging due to several features: (1) intrinsic dynamics; (2) close interaction between various system components; and (3) strong coupling of design, control, and operating conditions. These features lead to a variety of degrees of freedom, which make it difficult to use simple design and control rules for systems integration.To move towards optimal systems integration of adsorption chillers, this thesis provides appropriate models
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Verlag G. Mainz Ion Transport in HfO2
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Verlag G. Mainz Prediction of Reaction Rate Constants for the Synthesis of Microgels
The accurate prediction of reaction kinetics data, e.g., reaction rate constants, for the microgel synthesis is highly desired because its usage in model-based design approaches promises the development of more specialized microgels and enables new applications. The complexity and the diversity of the microgel synthesis, however, often prevent experimental approaches but depict challenges for prediction approaches, as well. Therefore, this thesis analyzes a wide range of aspects relevant for the microgel synthesis individually and proposes prediction strategies for each.Here, the focus is on three main aspects: (i) The prediction of reaction kinetics in homogenous liquid reaction environments by combining high-level density functional theory and COSMO-RS, (ii) improving the property prediction of ionic species by applying the Cluster-Continuum approach and analyzing the uncertainty of the reference data, and (iii) enabling the kinetics prediction for inhomogeneous reaction en
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Verlag G. Mainz Earth Abundant Metals in CH Activation and RingFormationOpening Reactions of Aromatic and NonAromatic Heterocycles
In the last decades, CH activation became an increasingly powerful tool for CC bond formation. It provided a valid alternative to conventional cross coupling reactions with maximised atom- and step-economy for synthetic reactions. Even though a lot of great advances have been made, some challenges in CH activations remain. CH bonds are highly stable (110 kcal/mol), often harsh reaction conditions are needed to break the bond and form a new CC compound. Furthermore, regioselectivity has been proven to be a difficult issue since a number of CH bonds are present in organic molecules. Also, chemoselectivity still remains a difficulty to overcome in CH activation reactions. Many groups focus their research on developing mild reaction conditions that proceed at ambient temperature, neutral conditions and in absence of strong oxidants or reductants.[1b] By choosing milder reaction conditions also problems of selectivity can be managed. In general, the catalytic cycle of CH activation react
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Verlag G. Mainz Measurement of Multicomponent Diffusion in Liquids Using Raman Microspectroscopy and Microfluidics
Diffusion is the rate-limiting mass transport step in many (bio)chemical processes. Diffusion data is therefore necessary to design unit operations, e.g., extraction. However, diffusion data on multicomponent mixtures in liquids are scarce, as diffusion measurements are intrinsically time-consuming and laborious. Also, several measurements are required for one diffusion coefficient matrix in a multicomponent mixture.Microfluidics promises to reduce experiment time and experimental effort, while Raman spectroscopy reduces the number of necessary experiments for multicomponent mixtures. To reduce the measurement effort for diffusion coefficients in multicomponent mixtures, microfluidics and Raman microspectroscopy were combined in this work for the first time for the measurement of diffusion coefficient matrices in multicomponent mixtures: Two liquids of different concentrations co-flow in parallel in a microfluidic H-cell, while changes of concentration due to diffusion are qu
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Verlag G. Mainz Studies of Tangible Cultural Heritage with Portable StrayField NMR
Sensors for stray-field nuclear magnetic resonance (NMR) have been employed to measure tangible cultural heritage since they were first conceived. Although NMR is a method with inherently low sensitivity and requires larger amounts of time than many other techniques, it is non-destructive and grants access to spin densities and relaxation times, physical quantities which are exclusive to the method. This thesis describes theory, instrumentation, and applications of unilateral NMR in the field of cultural heritage.The detection zone of an NMR-MOUSE, a sensor developed and maintained by past and present members of the group of Professor Blümich, is mapped through back-projection for the first time. Traditionally, the signal arising from the detection volume was averaged over multiple scans until the signal response was satisfactory. In this work, an algorithm is proposed to improve the signal-to-noise ratio in magnetization decays as a method of post processing an output, which
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Verlag G. Mainz A MilliliterScale Setup for the Efficient Characterization of Multicomponent VaporLiquid Equilibria Using Raman Spectroscopy
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Verlag G. Mainz Modelbased Design of Product Solvent and Process for Formic Acid Synthesis from CO2 and H2
Today humanity faces a challenge: Global warming that is caused by emissions of CO2. To reduce CO2 emissions, usage of CO2 as a renewable carbon source has gained attention. In particular, the CO2-based synthesis of formic acid has been intensively studied, since in addition to utilizingCO2, formic acid could also act as chemical storage of fluctuating renewable energy. Developing such storage is paramount for any renewable energy system due to the fluctuating occurrence of e.g. wind. However, for the CO2-based formic acid synthesis, only a few processes have been developed. Thus, novel formic acid synthesis processes are developed in this thesis. The development considers process structure and solvents, as well as formic acid derivatives due to the unfavorable equilibrium of the CO2-based formic acid synthesis.Firstly, a process is developed for the formic acid synthesis with the widely investigated solvent dimethyl sulfoxide (DMSO). The work identifies that DMSO has an azeo
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Verlag G. Mainz Hybrid DigitalAnalog Transmission Systems Design and Evaluation
During the last 25 years, most of the communication systems have been converted to purely digital technology, although the transmitted content mostly is analog by nature. The principal advantages of digital communication are compression by source encoding, bit error protection by channel coding and robust transmission over noisy channels by appropriate modulation. Digital systems are usually designed for worst case channel conditions. However, often the channel quality is much better, which is not reflected in an improved end-to-end transmission quality due to inevitable quantization noise produced by the source encoder.In this thesis, the focus is set on systems which: are not purely digital anymore benefit from increasing channel qualities and avoid the saturation effect using discrete-time, continuous-amplitude techniques.In the first part, purely analog, i.e., discrete-time and continuous-amplitude transmission systems are considered with line
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Verlag G. Mainz Immobilization of RutheniumTriphos Catalysts and their Application for the Hydrogenation of Polar Bonds in Batch and ContinuousFlow Systems
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Verlag G. Mainz Datadriven Modeling and Optimization of MultiEnergy Systems
Big data raises new opportunities for deep insights and supporting decision-making. To seize these opportunities, methods that derive useful knowledge from large amounts of data are needed. Such methods can help meet urgent challenges in many fields. An urgent challenge for energy systems is the necessary transformation towards sustainability to mitigate climate change. One crucial aspect of this challenge is a permanent optimal operation of energy systems. In principle, mathematical optimization can best determine the optimal operation of energy systems. However, manual model generation and operational optimization of energy systems are time-consuming and can thus prevent an application of mathematical optimization in practice. This thesis presents methods that use measured data to automatically generate mathematical models of energy systems to tackle the challenge of time-consuming model generations. Additionally, methods are presented that accelerate the operational optimization
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Verlag G. Mainz HD Telephony by Artificial Bandwidth Extension
The audio bandwidth of digital landline and mobile telephone networks is still mostly restricted to 200 Hz to 3.4 kHz. This is due to compatibility requirements during the transition phase from analogue to digital transmission technology. The resulting characteristic telephone speech is widely accepted, but the intelligibility of syllables is only 91%.Meanwhile, improved coding standards for so-called HD voice or Wideband Speech have been developed which are gradually being introduced into the networks. They support an audio frequency bandwidth of 50 Hz to 7.0 kHz with significantly increased audio quality and speech intelligibility. For a very long time however, new HD-telephones and old narrowband telephones have to co-exist. If an HD-terminal is connected over a narrowband link to an old telephone, the improved coding scheme cannot be used.In this thesis, signal processing concepts are developed for improving audio quality and intelligibility of narrowband speech by
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Verlag G. Mainz SystemWide Perspective for Life Cycle Assessment of CO based C1Chemicals
In recent years, the conversion of CO2 to basic chemicals with one carbon atom (C1-chemicals) such as methane and methanol has gained increasing interest. The major motivation for the utilization of CO2 is the reduction of global warming and fossil depletion impacts. However, these reductions are not guaranteed because all C1-chemicals require hydrogen besides the abundantly available CO2. Thus, the goal of this thesis is the life cycle assessment of CO2-based C1-chemicals (methane, methanol, carbon monoxide and formic acid). The assessment is based on a system-wide perspective, which means that for limited resources such as renewable electricity also the utilization of the limited resources is in other processes is considered.First of all, the CO2-based processes are compared to fossil-based processes for C1-chemicals. Formic acid has the highest potential to reduce global warming and fossil depletion impacts followed by carbon monoxide, methanol and methane. Even if hydroge
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Verlag G. Mainz HighCurrent Anode Phenomena in Vacuum Arcs
The emerging interest on the application of vacuum interrupter (VI) in medium and even high-voltage application has led to increase of comprehensive and fundamental research on VIs. Application of these interrupters is however hindered by limitation of interrupting capability, when high-current anode phenomena occur.The goal of the work is to investigate the high-current anode phenomena using spectroscopic methods se well as electrical measurements. Different current waveforms, i.e. AC and DC pulses are applied. Moreover, the impact of vacuum interrupter properties, e.g. electrode diameter and geometries, contact materials, opening time and opening speed on the formation of high-current anode phenomena are investigated.The results reveal that the threshold current of the high-current anode formation is dominated by the current in case of high-frequency pulsed, whereas in case of pulsed DC, it is controlled by transferred charge.Along with typical and already kno
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Verlag G. Mainz From LifeCycle Assessment towards LifeCycle Design of Carbon Dioxide Capture and Utilization
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Verlag G. Mainz Adaption of new strategies for parameterization of a microstructurebased flow stress model
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Verlag G. Mainz Analysis of CSMA Based Broadcast Communication in Vehicular Networks with Hidden Stations
This thesis studies the congestion problem at the Medium Access Control (MAC) layer of the IEEE 802.11p system in highway scenarios using an analytical approach. Using the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol, the IEEE 802.11p system suffers from the hidden station problem. This thesis provides formal definitions for the hidden station condition and the hidden station problem and develops an analytical methodology for CSMA protocols to investigate the interaction between stations in mutual channel sensing range and hidden to each other. Analytical models are developed for broadcast communication using the generic CSMA protocol and the IEEE 802.11p MAC protocol with a one-dimensional (1-D) homogeneous network topology. Simulation studies prove the accuracy of the models in analyzing the reliability performance and the efficiency performance of CSMA broadcast communication with hidden stations.The performance of Cooperative Awareness Message (CAM
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Verlag G. Mainz LifeCycle Assessment of LowCarbon Technologies from Screening to Integrated Energy System Design
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Verlag G. Mainz Decarbonization of Copper Production by Optimal Demand Response and PowertoHydrogen
To avoid greenhouse gas (GHG) emissions and mitigate climate change, low-carbon technologies must be used to provide renewable energy and replace fossil fuels. However, this system transition is very material-intensive and leads to high demand for critical materials. Copper is such a material that is essential for electrical applications and many low-carbon technologies. The production of copper itself is an energyintensive process. Thus, two challenges arise that are addressed in this thesis: the flexible process operation in a fluctuating renewable energy system and the avoidance of process-based GHG emissions.The flexible operation of electricity-intensive processes can support the power grid and provide economic benefits. Demand response (DR) describes operational adjustments based on an economic incentive, such as fluctuating electricity prices. Our initial analysis shows a large DR potential of two electricity-intensive process steps in copper production. To consider th
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Verlag G. Mainz Artificial Metalloproteins for NonNatural Reactions
Organometallic chemistry has shown tremendous success in developing new metal catalysts for industrial applications, e.g. polymerization, organic synthesis or fine chemical synthesis. Nowadays, several active and selective catalysts are known and still, the issue of activity and selectivity remains a challenge. Nature has solved this issue by evolving selective enzymes. These enzymes have excellent catalytic properties with high substrate specificity and product selectivity due to their specialized active site. However, the advantage of high product selectivity comes at the cost of a limited substrate scope. The shape of the active site is crucial for selectivity since it is responsible for highly efficient substrate recognition and orientation together with stabilization of reactive intermediates. The number of enzymatic processes in industry increased due to an increased demand of enantiopure products. The concept of biohybrid catalysts, also named artificial metalloproteins/-enzy
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Verlag G. Mainz Novel Concepts for Iron and Manganesecatalyzed Homogenous Redox Transformations
Transition metal catalysis plays a crucial role in the development of new chemical transformations, which can be broadly applied in organic synthesis, medicinal chemistry, synthesis of biologically relevant molecules, pharmaceuticals and other related fields. In recent years, the need for application of sustainable methods is significantly growing due to the necessity of waste-free transformations. Plenty of industrially run processes still apply classical procedures, which often lead to production of tons of waste as a consequence of multistep synthesis. Thus, development of novel catalytic systems which would afford complex molecular structures via straightforward processes is still desired. Hence, metal-catalyzed transformations play a crucial role in the development of new synthetic strategies, as they can easily lead to the reduction of synthetic steps and, ipso facto, reduction of waste leading to atom-economic transformations. Application of transition metals particularly in
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Verlag G. Mainz ContinuousAmplitude Error Protection of DiscreteTime Signals
Transmitting analog audio, video, or sensor data with a digital system requires sampling and quantization. While a sampled bandlimited signal can be reconstructed perfectly if the Nyquist-Shannon sampling theorem is met, quantization unavoidably adds irreversible errors. Given a certain bitrate for quantization (or source coding in general), the achievable signal quality is therefore limited. Transmission of the signal over a noisy channel causes additional errors. If some part of the bitrate is used for protecting the signal with a channel code, these additional errors can be reduced or even eliminated. However, this reduces the achievable maximum quality if the gross bitrate is fixed. Since this compromise between quantization and channel coding is often designed for the worst-case channel, the signal quality saturates early with increasing channel quality, and transmission over a better channel is far below optimum.Instead of conventional digital systems, this thesis cover
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Verlag G. Mainz Advances in lowfield NMR relaxometry
In the context of this work, three unilateral NMR sensors were designed, constructed and characterized. For the new sensors, the concept was chosen to vary the angle of the polarization of the magnets. This affects the size and the position of the sensitive slice. The MOUSEPAD, based on the modified design of the Profile NMR-MOUSE with 5 mm penetration depth, achieved a penetration depth of 17 mm. The Mini-MOUSEPAD is based on the Mini-MOUSE and has an increased penetration depth of 2.5 mm. The penetration depth is a crucial parameter for investigations with unilateral NMR, since the object of interest can be arbitrary shaped and the relevant areas at higher depths might be difficult to access. Therefore, these sensors might show a strategy for further miniaturization of state-of-the-art unilateral NMR sensors. The special magnet arrangement of both sensors results in a reduction of the magnetic field strenght (4.9MHz for the MOUSEPAD and 9.0 MHz for the Mini-MOUSEPAD) and much lowe
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Verlag G. Mainz Assessment of Adsorbents for Drying by Experiments and Dynamic Simulations
In order to slow down global warming, greenhouse gas emissions must be reduced. Human-caused greenhouse gas emissions come primarily from consumption of fossil energy. In order to reduce the consumption of fossil energy, the demand is rising for energy-efficient technologies. One promising energy-efficient technology is the adsorption dishwasher that was commercialized recently. The use of adsorbents enabled the adsorption dishwasher to save 25% of energy compared to a conventional dishwasher. To increase the savings and to further enhance the entire process, the adsorption dishwasher should be improved. The improvement should foremost focus on the adsorbents, since adsorbents are the key of this energy-efficient technology.This thesis therefore assesses adsorbents for the application in an adsorption dishwasher. The assessment is carried out both experimentally and theoretically. Theoretical investigations are divided in 3 stages of complexity:Stage 1 is a static anal
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Verlag G. Mainz On the Aspects of crash Box Performance from Material Perspective
The increasing worldwide concerns about the danger of climate change have pushed goverments to strictly regulate CO2 emissions of automobiles. This development has led the auto industry to focus on design concepts that can reduce fuel consumption, and subsequently emissions. The power generation and tranmission systems, which lead the fuel consumption inefficiency in a car, are the leading factors for high emissions. The conventionally bulky structure of automobiles comes second. Thus improvements on autobody design can decrease the emissions significantly.
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Verlag G. Mainz Advances in biomedical NMR with spatial resolution
In modern medicine, magnetic resonance imaging (MRI) is an essential diagnostic tool, which enables physicians to detect a great variety of diseases and physical injuries. The scope of possibilities encompasses neuro-, cardiovascular-, musculoskeletal-, hepatobiliary- and gastrointestinal imaging as well a magnetic resonance angiography. Besides commercially available MRI scanners, low magnetic field devices gain more and more attention because they are more compact, mostly portable, easier to handle due to the lack of cryogenic coolants, and usually come with a large cost saving.In this thesis, high magnetic field devices and unilateral NMR sensors are deployed to explore different biomedical topics. Imaging techniques are used to study the flow inside aneurysmsenlargements of blood vessels in the human body, whose rupture can lead to severe health issues. In an experimental flow set-up, different fluids and flow velocities are tested inside silicon aneurysm models with and
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Verlag G. Mainz Robust Dynamic Optimization and Control of SemiBatch Processes under Parametric Uncertainties
Optimal operation and control of batch and semi-batch processes has an increasing importance in the chemical process industry. However, the solution of dynamic uncertainties in the process model might lead to a high risk of constraint violations. In order to solve the dynamic optimization problem under parametric uncertainty, four different approaches are investigated in this work. Thereafter, two of them are used in a multi-scenario eNMPC in order to robustly control batch processes under parametric uncertainties.
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Verlag G. Mainz A Design Approach for Adsorption Energy Systems Integrating Dynamic Modeling with SmallScale Experiments
Adsorption energy systems can be driven by thermal energy from waste heat or the sun and thereby allow reducing fossil energy consumption and thus reduce global greenhouse gas emissions. Adsorption heat pumps and chillers can provide heating or cooling, adsorption thermal energy storage allows storing thermal energy. However, adsorption energy systems suffer from high investment costs due to low performance.Performance of adsorption energy systems strongly depends on the equilibrium properties of the working pair as well as heat and mass transfer mechanisms of the adsorption material in the adsorption energy system (adsorbent configuration).Evaluating new working pairs and adsorbent configurations is rather challenging: While the working pair''s equilibrium properties can be determined with standardized measurement equipment, heat and mass transfer mechanisms cannot easily be determined, since they strongly depend on the full-scale adsorption energy system. Constructio
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Verlag G. Mainz Experiments and Validated Models for Adsorption Thermal Energy Storage in Industrial and Residential Applications
Thermal energy storage (TES) helps to reduce energy consumption and peak demands by balancing heat supply and demand on all time scales from short-term to seasonal. Thus, TES is an important technology to improve flexibility and efficiency of energy systems. In particular, adsorption TES systems, which exploit the enthalpy of adsorption, provide high energy storage density and high efficiency.The present thesis therefore analyzes an adsorption TES unit for residential and industrial applications. Industrial energy supply can be made more efficient by integrating waste heat into the process heat supply and by using energy-efficient technologies. Adsorption TES contributes to both approaches: waste heat can be integrated via the heat pump effect and TES allows for energy-efficient cogeneration heat supply for batch processes.We evaluate the energy efficiency of the heat supply for an industrial batch process by adsorption TES and cogeneration. To evaluate the performance
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Verlag G. Mainz Wind Noise Reduction
With the technological progress, devices, such as mobile phones, tablet computers or hearing aids, can be used in a large variety of every-day situations for mobile communication. Acoustic background noise signals, which are picked up with the desired speech signal, can impair the signal quality and the intelligibility of a conversation. A special noise type is generated outdoors, if the microphone is exposed to a wind stream resulting in strong-rumbling noise, which is highly non-stationary. As a result, conventional approaches for noise reduction fail in the case of noise induced by wind turbulences.This thesis is focused on the development of signal processing concepts, which reduce the undesired effects of wind noise. The key contributions are: Signal analysis of wind noise Digital signal model for wind noise generation Signal processing algorithms for detection and reduction of wind noise signals.All these topics are considered with the focus
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Verlag G. Mainz Options for the Joint Evolution of Digital Terrestrial Television and Mobile Internet Access
Terrestrial broadcast is traditionally realized over High Tower High Power (HTHP) networks which have been preserved in the transition from the analog PAL to the first generation of the digital DVB-T technology. The drawback of this traditional network design is its spectral inefficiency. The demand for providing more TV programs with HD quality as well as the increasing spectrum consumption of mobile internet services, with video streaming being one of the driving factors, necessitate a re-optimization of the current broadcast network and a more efficient allocation of frequencies.In this thesis, three options for a future frequency-efficient evolution and coexistence of terrestrial TV and mobile internet are specified and investigated: Transition from the current terrestrial broadcast with DVB-T to its successor DVB-T2 while retaining the HTHP network infrastructure Switch-over from DVB-T to DVB-T2 with transition to a Low Tower Low Power (LTLP) network infras
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Verlag G. Mainz Development of Methodologies in Organic Synthesis for BaseCatalysed CC Bond Formation Trifluoromethylthiolation and for Photocatalysis in Flow
Synthetic organic chemistry aims toward the development of methods for the practical synthesis of important molecules such as bioactive ingredients, pesticides, dyes, and polymers. Although extraction of organic molecules from natural resources is possible, organic synthesis often provides a cheaper and more practical access to them from readily accessible starting materials, as well as the possibility to artificially modify the structure of naturally-occurring molecules to increase their activity or modulate their properties. In medicinal chemistry, a standard approach to find the most potent active ingredient is the so-called combinatorial sythesis strategy: after identification of a promising structure, often a small molecule found in nature, a library of compounds with different substitution patterns is prepared and tested to find the bist hit.
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Verlag G. Mainz VoIP Performance of LTE Networks
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